Need your advice guys, I noticed that water enters the boot and I think it's coming from under the boot seal. Previously it has silicone sealer under the boot seal which I removed because it ate into the paint and caused it to rust. Do I need to reapply some sort of sealer between the metal lip and seal to stop the leak and if so which type is safe to use on paint etc. has anyone else had this issue? Cheers.
Mine was the 3rd brake light too, bought a new seal £33 but that still leaked as it was extremely thin, I ended up using a thicker seal which I made fit perfectly and this cured the problem.
Only hand-wash the car, avoid directing the power washer on the gap between boot lid and the rest of the car. This should help. Also look into the brake light seal. Where does the water enter, can you see a trail?
Your Majesty had a similar problem and found that parking it so that it faced downhill worked. Leak in boot solved!!! It might be worth a try.